Avian erythrocytes extrude substantial quantities of cyclic AMP in response to beta-adrenergic stimulation. We have found that several metabolic inhibitors, prostaglandins, and temperatures below 22 degrees inhibit cyclic AMP extrusion. We plan to determine the energy dependence of the efflux, to describe it mechanistically by kinetic studies and to assess the contribution to cyclic AMP efflux of other transport systems and of enzymes that interact with cyclic AMP (adenylate cyclase, phosphodiesterase, protein kinase). We will investigate the interaction of prostaglandins and other drugs and hormones as inhibitors of cyclic AMP efflux, assessing the specificity of the prostaglandins' effects by studying several other transmembrane events. To describe the role of membrane fluidity in the modulation of cyclic AMP efflux by prostaglandin and temperature, we will estimate membrane viscosity by fluorescence polarization technics using diphenylhexatriene as a fluorophore. Since cyclic AMP-dependent protein kinases are probably activated when a cell is stimulated to produce and extrude cyclic AMP, we will also consider the roles of membrane bound protein kinases and the phosphorylation of endogenous membrane substrates in cyclic AMP extrusion and its regulation. We will attempt to identify components of the cyclic AMP transport mechanism by photo-affinity labelling using 8-azido-cyclic AMP. We will extend our studies of cyclic AMP efflux to mammalian reticulocytes. The presence or absence of the extrusion capacity in these cells and in mammalian red cells will be interesting in light of previously described changes in beta-adrenergic receptors and hormonally sensitive adenylate cyclase that accompany maturation of the reticulocyte.